The Rugby Championship kicks off for 2017 this weekend, starting with old foes New Zealand and Australia facing off in a match that doubles as the first of the three-match Bledisloe Cup series. So where will the two matches be played, what time do they kick off, and who will feature?

Unbeaten fighter Floyd Mayweather has promised to repay any losses talk-show host Jimmy Kimmel suffers if he loses his fight against Conor McGregor.

Four O'Brien-trained horses and the Kavanagh-trained Magicool returned levels of cobalt above the 200 micrograms per litre of urine threshold in 2014.

Counsel for the trainers, Damian Sheales, has compared the proceedings against his clients to the Salem witch trials.

O'Brien on Wednesday reiterated his criticisms of Racing Victoria's handling of the investigation into elevated cobalt levels.

"We've raised some real issues about how this scenario's played out over the last 12 months," he said.

"We still haven't had any answers ... the chief integrity officer has gone missing."

The trainers hope by going to VCAT they will be able to subpoena and question officials.

O'Brien has expressed disappointment that counsel was unable to cross examine Racing Victoria chief steward Terry Bailey and Dion Villella, from RV's Compliance and Assurance Team, during the seven-day hearing into the charges against them.

"At the end of the day they're really only holding back the tide for when we get to VCAT and everything is examined properly in a real, adult court," O'Brien said.